packer: Convert from JSON to HCL

As of version 1.7.0, HCL2 is the preferred way to write Packer
templates. The documentation reflect this and it is easier if we use the
preferred format.

README.md

@@ -45,7 +45,7 @@ tasks.
 We use packer to build snapshots on hcloud to use as server base images.
 In order to use this, you need to install packer and then run
 
-    packer build -var $(misc/get_key.py misc/vaults/vault_hetzner.yml hetzner_cloud_api_key --format env) packer/archlinux.json
+    packer build -var $(misc/get_key.py misc/vaults/vault_hetzner.yml hetzner_cloud_api_key --format env) packer/archlinux.pkr.hcl
 
 This will take some time after which a new snapshot will have been created on the primary hcloud archlinux project.
 

packer/archlinux.json

-{
-    "variables": {
-        "hetzner_cloud_api_key": null
-    },
-    "sensitive-variables": ["hetzner_cloud_api_key"],
-    "builders": [{
-        "type": "hcloud",
-        "snapshot_name": "archlinux-{{ isotime \"2006-01-02T15:04\" }}",
-        "snapshot_labels": {
-            "custom_image": "archlinux"
-        },
-        "token": "{{ user `hetzner_cloud_api_key` }}",
-        "image": "ubuntu-22.04",
-        "server_type": "cx11",
-        "ssh_username": "root",
-        "location": "fsn1",
-        "rescue": "linux64"
-    }],
-    "provisioners": [{
-        "type": "ansible",
-        "playbook_file": "playbooks/tasks/install_arch.yml",
-        "host_alias": "packer-base-image",
-        "inventory_directory": ".",
-        "use_proxy": false
-    }]
-}

packer/archlinux.pkr.hcl

+# https://www.packer.io/docs/templates/hcl_templates/blocks/packer
+packer {
+  required_plugins {
+    ansible = {
+      source  = "github.com/hashicorp/ansible"
+      version = ">= 1.1.0"
+    }
+    hcloud = {
+      source  = "github.com/hashicorp/hcloud"
+      version = ">= 1.0.0"
+    }
+  }
+}
+
+# https://www.packer.io/docs/templates/hcl_templates/variables#type-constraints
+variable "hetzner_cloud_api_key" {
+  type      = string
+  sensitive = true
+}
+
+# https://www.packer.io/docs/templates/hcl_templates/blocks/source
+source "hcloud" "rescue" {
+  image       = "ubuntu-22.04"
+  location    = "fsn1"
+  rescue      = "linux64"
+  server_type = "cx11"
+  snapshot_labels = {
+    custom_image = "archlinux"
+  }
+  snapshot_name = "archlinux-${timestamp()}"
+  ssh_username  = "root"
+  token         = var.hetzner_cloud_api_key
+}
+
+# https://www.packer.io/docs/templates/hcl_templates/blocks/build
+build {
+  sources = ["source.hcloud.rescue"]
+
+  provisioner "ansible" {
+    host_alias          = "packer-base-image"
+    inventory_directory = "."
+    playbook_file       = "playbooks/tasks/install_arch.yml"
+    use_proxy           = false
+  }
+}